1
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Asghari P, Scriven DR, Shahrasebi S, Valdivia HH, Alsina KM, Valdivia CR, Navarro-Garcia JA, Wehrens XH, Moore ED. Phosphorylation of RyR2 simultaneously expands the dyad and rearranges the tetramers. J Gen Physiol 2024; 156:e202213108. [PMID: 38385988 PMCID: PMC10883851 DOI: 10.1085/jgp.202213108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 01/23/2023] [Accepted: 01/31/2024] [Indexed: 02/23/2024] Open
Abstract
We have previously demonstrated that type II ryanodine receptors (RyR2) tetramers can be rapidly rearranged in response to a phosphorylation cocktail. The cocktail modified downstream targets indiscriminately, making it impossible to determine whether phosphorylation of RyR2 was an essential element of the response. Here, we used the β-agonist isoproterenol and mice homozygous for one of the following clinically relevant mutations: S2030A, S2808A, S2814A, or S2814D. We measured the length of the dyad using transmission electron microscopy (TEM) and directly visualized RyR2 distribution using dual-tilt electron tomography. We found that the S2814D mutation, by itself, significantly expanded the dyad and reorganized the tetramers, suggesting a direct link between the phosphorylation state of the tetramer and its microarchitecture. S2808A and S2814A mutant mice, as well as wild types, had significant expansions of their dyads in response to isoproterenol, while S2030A mutants did not. In agreement with functional data from these mutants, S2030 and S2808 were necessary for a complete β-adrenergic response, unlike S2814 mutants. Additionally, all mutants had unique effects on the organization of their tetramer arrays. Lastly, the correlation of structural with functional changes suggests that tetramer-tetramer contacts play an important functional role. We thus conclude that both the size of the dyad and the arrangement of the tetramers are linked to the state of the channel tetramer and can be dynamically altered by a β-adrenergic receptor agonist.
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Affiliation(s)
- Parisa Asghari
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, Canada
| | - David R.L. Scriven
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, Canada
| | - Saba Shahrasebi
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, Canada
| | - Hector H. Valdivia
- Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA
| | | | - Carmen R. Valdivia
- Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA
| | - J. Alberto Navarro-Garcia
- Department of Integrative Physiology, Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX, USA
| | - Xander H.T. Wehrens
- Department of Integrative Physiology, Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX, USA
| | - Edwin D.W. Moore
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, Canada
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2
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Zhang Y, Asghari P, Scriven DRL, Moore EDW, Chou KC. 3D structured illumination microscope using a spinning disk [Invited]. BIOMEDICAL OPTICS EXPRESS 2023; 14:5710-5719. [PMID: 38021136 PMCID: PMC10659796 DOI: 10.1364/boe.499181] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 09/19/2023] [Accepted: 10/03/2023] [Indexed: 12/01/2023]
Abstract
Three-dimensional (3D) structured illumination microscopy (SIM) improves spatial resolution by a factor of two in both lateral and axial directions. However, the adoption of 3D SIM is limited by low imaging speed, susceptibility to out-of-focus light, and likelihood of reconstruction errors. Here we present a novel approach for 3D SIM using a spinning disk. The disk generates a 3D lattice illumination pattern on the sample and optically reconstructs super-resolved images in real time. This technique achieves a 2-times resolution improvement with a speed up to 100 frames per second while physically rejecting 90% of the background signal.
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Affiliation(s)
- Youchang Zhang
- Department of Chemistry, Life Sciences Institute, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
| | - Parisa Asghari
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - David R L Scriven
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Edwin D W Moore
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Keng C Chou
- Department of Chemistry, Life Sciences Institute, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
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3
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Zhang Y, Asghari P, Scriven DRL, Moore EDW, Chou KC. Structured illumination microscopy with a phase-modulated spinning disk for optical sectioning. OPTICS LETTERS 2023; 48:3933-3936. [PMID: 37527086 DOI: 10.1364/ol.494655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Accepted: 06/26/2023] [Indexed: 08/03/2023]
Abstract
Among various super-resolution microscopic techniques, structured illumination microscopy (SIM) stands out for live-cell imaging because of its higher imaging speed. However, conventional SIM lacks optical sectioning capability. Here we demonstrate a new, to the best of our knowledge, approach using a phase-modulated spinning disk (PMSD) that enhances the optical sectioning capability of SIM. The PMSD consists of a pinhole array for confocal imaging and a transparent polymer layer for light phase modulation. The light phase modulation was designed to cancel the zeroth-order diffracted beam and create a sharp lattice illumination pattern using the interference of four first-order diffracted beams. In the detection optical path, the PMSD serves as a spatial filter to physically reject about 80% of the out-of-focus signals, an approach that allows for real-time optical reconstruction of super-resolved images with enhanced contrast. Furthermore, the simplicity of the design makes it easy to upgrade a conventional fluorescence microscope to a PMSD SIM system.
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4
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Asghari P, Scriven DRL, Shahrasebi S, Valdivia HH, Wehrens XHT, Moore EDW. PHOSPHORYLATION OF RyR2 SIMULTANEOUSLY EXPANDS THE DYAD AND REARRANGES THE TETRAMERS. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.23.541024. [PMID: 37292875 PMCID: PMC10245935 DOI: 10.1101/2023.05.23.541024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We have previously demonstrated that type II ryanodine receptors (RyR2) tetramers can be rapidly rearranged in response to a phosphorylation cocktail. The cocktail modified downstream targets indiscriminately making it impossible to determine whether phosphorylation of RyR2 was an essential element of the response. We therefore used the β-agonist isoproterenol and mice with one of the homozygous mutations, S2030A +/+ , S2808A +/+ , S2814A +/+ , or S2814D +/+ , to address this question and to elucidate the role of these clinically relevant mutations. We measured the length of the dyad using transmission electron microscopy (TEM) and directly visualized RyR2 distribution using dual-tilt electron tomography. We found that: 1) The S2814D mutation, by itself, significantly expanded the dyad and reorganized the tetramers suggesting a direct link between the phosphorylation state of the tetramer and the microarchitecture. 2) All of the wild-type, as well as the S2808A and S2814A mice, had significant expansions of their dyads in response to ISO, while S2030A did not. 3) In agreement with functional data from the same mutants, S2030 and S2808 were necessary for a complete β-adrenergic response, whereas S2814 was not. 4) All the mutated residues had unique effects on the organization of their tetramer arrays. 5) The correlation of structure with function suggests that tetramer-tetramer contacts play an important functional role. We conclude that both the size of the dyad and the arrangement of the tetramers are linked to the state of the channel tetramer and can be dynamically altered by a β-adrenergic receptor agonist. Summary Analysis of RyR2 mutants suggests a direct link between the phosphorylation state of the channel tetramer and the microarchitecture of the dyad. All phosphorylation site mutations produced significant and unique effects on the structure of the dyad and its response to isoproterenol.
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5
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Dixon RE. Nanoscale Organization, Regulation, and Dynamic Reorganization of Cardiac Calcium Channels. Front Physiol 2022; 12:810408. [PMID: 35069264 PMCID: PMC8769284 DOI: 10.3389/fphys.2021.810408] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2021] [Accepted: 11/30/2021] [Indexed: 12/19/2022] Open
Abstract
The architectural specializations and targeted delivery pathways of cardiomyocytes ensure that L-type Ca2+ channels (CaV1.2) are concentrated on the t-tubule sarcolemma within nanometers of their intracellular partners the type 2 ryanodine receptors (RyR2) which cluster on the junctional sarcoplasmic reticulum (jSR). The organization and distribution of these two groups of cardiac calcium channel clusters critically underlies the uniform contraction of the myocardium. Ca2+ signaling between these two sets of adjacent clusters produces Ca2+ sparks that in health, cannot escalate into Ca2+ waves because there is sufficient separation of adjacent clusters so that the release of Ca2+ from one RyR2 cluster or supercluster, cannot activate and sustain the release of Ca2+ from neighboring clusters. Instead, thousands of these Ca2+ release units (CRUs) generate near simultaneous Ca2+ sparks across every cardiomyocyte during the action potential when calcium induced calcium release from RyR2 is stimulated by depolarization induced Ca2+ influx through voltage dependent CaV1.2 channel clusters. These sparks summate to generate a global Ca2+ transient that activates the myofilaments and thus the electrical signal of the action potential is transduced into a functional output, myocardial contraction. To generate more, or less contractile force to match the hemodynamic and metabolic demands of the body, the heart responds to β-adrenergic signaling by altering activity of calcium channels to tune excitation-contraction coupling accordingly. Recent accumulating evidence suggests that this tuning process also involves altered expression, and dynamic reorganization of CaV1.2 and RyR2 channels on their respective membranes to control the amplitude of Ca2+ entry, SR Ca2+ release and myocardial function. In heart failure and aging, altered distribution and reorganization of these key Ca2+ signaling proteins occurs alongside architectural remodeling and is thought to contribute to impaired contractile function. In the present review we discuss these latest developments, their implications, and future questions to be addressed.
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Affiliation(s)
- Rose E Dixon
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, Davis, CA, United States
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6
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Arslanova A, Shafaattalab S, Ye K, Asghari P, Lin L, Kim B, Roston TM, Hove-Madsen L, Van Petegem F, Sanatani S, Moore E, Lynn F, Søndergaard M, Luo Y, Chen SRW, Tibbits GF. Using hiPSC-CMs to Examine Mechanisms of Catecholaminergic Polymorphic Ventricular Tachycardia. Curr Protoc 2021; 1:e320. [PMID: 34958715 DOI: 10.1002/cpz1.320] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a potentially lethal inherited cardiac arrhythmia condition, triggered by physical or acute emotional stress, that predominantly expresses early in life. Gain-of-function mutations in the cardiac ryanodine receptor gene (RYR2) account for the majority of CPVT cases, causing substantial disruption of intracellular calcium (Ca2+ ) homeostasis particularly during the periods of β-adrenergic receptor stimulation. However, the highly variable penetrance, patient outcomes, and drug responses observed in clinical practice remain unexplained, even for patients with well-established founder RyR2 mutations. Therefore, investigation of the electrophysiological consequences of CPVT-causing RyR2 mutations is crucial to better understand the pathophysiology of the disease. The development of strategies for reprogramming human somatic cells to human induced pluripotent stem cells (hiPSCs) has provided a unique opportunity to study inherited arrhythmias, due to the ability of hiPSCs to differentiate down a cardiac lineage. Employment of genome editing enables generation of disease-specific cell lines from healthy and diseased patient-derived hiPSCs, which subsequently can be differentiated into cardiomyocytes. This paper describes the means for establishing an hiPSC-based model of CPVT in order to recapitulate the disease phenotype in vitro and investigate underlying pathophysiological mechanisms. The framework of this approach has the potential to contribute to disease modeling and personalized medicine using hiPSC-derived cardiomyocytes. © 2021 Wiley Periodicals LLC.
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Affiliation(s)
- Alia Arslanova
- Cellular and Regenerative Medicine Centre, British Columbia Children's Hospital Research Institute, Vancouver, British Columbia, Canada.,Molecular Cardiac Physiology Group, Departments of Biomedical Physiology and Kinesiology and Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Sanam Shafaattalab
- Cellular and Regenerative Medicine Centre, British Columbia Children's Hospital Research Institute, Vancouver, British Columbia, Canada.,Molecular Cardiac Physiology Group, Departments of Biomedical Physiology and Kinesiology and Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Kevin Ye
- Cellular and Regenerative Medicine Centre, British Columbia Children's Hospital Research Institute, Vancouver, British Columbia, Canada.,Molecular Cardiac Physiology Group, Departments of Biomedical Physiology and Kinesiology and Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Parisa Asghari
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Lisa Lin
- Cellular and Regenerative Medicine Centre, British Columbia Children's Hospital Research Institute, Vancouver, British Columbia, Canada.,Molecular Cardiac Physiology Group, Departments of Biomedical Physiology and Kinesiology and Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - BaRun Kim
- Molecular Cardiac Physiology Group, Departments of Biomedical Physiology and Kinesiology and Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Thomas M Roston
- British Columbia Children's Hospital Heart Center, Vancouver, British Columbia, Canada
| | - Leif Hove-Madsen
- Cardiac Rhythm and Contraction Group, IIBB-CSIC, CIBERCV, IIB Sant Pau, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
| | - Filip Van Petegem
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Shubhayan Sanatani
- British Columbia Children's Hospital Heart Center, Vancouver, British Columbia, Canada
| | - Edwin Moore
- Cardiac Rhythm and Contraction Group, IIBB-CSIC, CIBERCV, IIB Sant Pau, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
| | - Francis Lynn
- Cellular and Regenerative Medicine Centre, British Columbia Children's Hospital Research Institute, Vancouver, British Columbia, Canada
| | | | - Yonglun Luo
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - S R Wayne Chen
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, University of Calgary, Calgary, Alberta, Canada
| | - Glen F Tibbits
- Cellular and Regenerative Medicine Centre, British Columbia Children's Hospital Research Institute, Vancouver, British Columbia, Canada.,Molecular Cardiac Physiology Group, Departments of Biomedical Physiology and Kinesiology and Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada.,School of Biomedical Engineering, University of British Columbia, Vancouver, British Columbia, Canada
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7
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Medvedev R, Sanchez-Alonso JL, Alvarez-Laviada A, Rossi S, Dries E, Schorn T, Abdul-Salam VB, Trayanova N, Wojciak-Stothard B, Miragoli M, Faggian G, Gorelik J. Nanoscale Study of Calcium Handling Remodeling in Right Ventricular Cardiomyocytes Following Pulmonary Hypertension. Hypertension 2020; 77:605-616. [PMID: 33356404 DOI: 10.1161/hypertensionaha.120.14858] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Pulmonary hypertension is a complex disorder characterized by pulmonary vascular remodeling and right ventricular hypertrophy, leading to right heart failure. The mechanisms underlying this process are not well understood. We hypothesize that the structural remodeling occurring in the cardiomyocytes of the right ventricle affects the cytosolic Ca2+ handling leading to arrhythmias. After 12 days of monocrotaline-induced pulmonary hypertension in rats, epicardial mapping showed electrical remodeling in both ventricles. In myocytes isolated from the hypertensive rats, a combination of high-speed camera and confocal line-scan documented a prolongation of Ca2+ transients along with a higher local Ca2+-release activity. These Ca2+ transients were less synchronous than in controls, likely due to disorganized transverse-axial tubular system. In fact, following pulmonary hypertension, hypertrophied right ventricular myocytes showed significantly reduced number of transverse tubules and increased number of axial tubules; however, Stimulation Emission Depletion microscopy demonstrated that the colocalization of L-type Ca2+ channels and RyR2 (ryanodine receptor 2) remained unchanged. Finally, Stimulation Emission Depletion microscopy and super-resolution scanning patch-clamp analysis uncovered a decrease in the density of active L-type Ca2+ channels in right ventricular myocytes with an elevated open probability of the T-tubule anchored channels. This may represent a general mechanism of how nanoscale structural changes at the early stage of pulmonary hypertension impact on the development of the end stage failing phenotype in the right ventricle.
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Affiliation(s)
- Roman Medvedev
- From the Dipartimento di Cardiochirurgia, Università degli Studi di Verona, Ospedale Borgo Trento, Italy (R.M., G.F.).,National Heart and Lung Institute, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom (R.M., J.L.S.-A., A.A.-L., E.D., V.B.A.S., B.W.-S., J.G.).,Humanitas Clinical and Research Center, Rozzano, Italy (R.M., T.S., M.M.)
| | - Jose L Sanchez-Alonso
- National Heart and Lung Institute, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom (R.M., J.L.S.-A., A.A.-L., E.D., V.B.A.S., B.W.-S., J.G.)
| | - Anita Alvarez-Laviada
- National Heart and Lung Institute, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom (R.M., J.L.S.-A., A.A.-L., E.D., V.B.A.S., B.W.-S., J.G.)
| | - Stefano Rossi
- Dipartimento di Medicina e Chirurgia, Università degli Studi di Parma, Italy (S.R., M.M.)
| | - Eef Dries
- National Heart and Lung Institute, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom (R.M., J.L.S.-A., A.A.-L., E.D., V.B.A.S., B.W.-S., J.G.).,Lab of Experimental Cardiology, University of Leuven, Belgium (E.D.)
| | - Tilo Schorn
- Humanitas Clinical and Research Center, Rozzano, Italy (R.M., T.S., M.M.)
| | - Vahitha B Abdul-Salam
- National Heart and Lung Institute, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom (R.M., J.L.S.-A., A.A.-L., E.D., V.B.A.S., B.W.-S., J.G.)
| | - Natalia Trayanova
- Department of Biomedical Engineering and Alliance for Cardiovascular Diagnostic and Treatment Innovation; Johns Hopkins University; Baltimore, MD (N.T.)
| | - Beata Wojciak-Stothard
- National Heart and Lung Institute, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom (R.M., J.L.S.-A., A.A.-L., E.D., V.B.A.S., B.W.-S., J.G.)
| | - Michele Miragoli
- Dipartimento di Medicina e Chirurgia, Università degli Studi di Parma, Italy (S.R., M.M.)
| | | | - Julia Gorelik
- National Heart and Lung Institute, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom (R.M., J.L.S.-A., A.A.-L., E.D., V.B.A.S., B.W.-S., J.G.)
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8
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Spinozzi S, Liu C, Chen Z, Feng W, Zhang L, Ouyang K, Evans SM, Chen J. Nexilin Is Necessary for Maintaining the Transverse-Axial Tubular System in Adult Cardiomyocytes. Circ Heart Fail 2020; 13:e006935. [PMID: 32635769 PMCID: PMC7583668 DOI: 10.1161/circheartfailure.120.006935] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Accepted: 03/31/2020] [Indexed: 01/28/2023]
Abstract
BACKGROUND NEXN (nexilin) is a protein of the junctional membrane complex required for development of cardiac T-tubules. Global and cardiomyocyte-specific loss of Nexn in mice leads to a rapidly progressive dilated cardiomyopathy and premature death. Therefore, little is known as to the role of NEXN in adult cardiomyocytes. Transverse-axial tubular system remodeling are well-known features in heart failure. Although NEXN is required during development for T-tubule formation, its role, if any, in mature T-tubules remains to be addressed. METHODS Nexn inducible adult cardiomyocyte-specific KO mice were generated. Comprehensive morphological and functional analyses were performed. Heart samples (n>3) were analyzed by molecular, biochemical, and electron microscopy analyses. Isolated single adult cardiomyocytes were analyzed by confocal microscopy, and myocyte shortening/re-lengthening and Ca2+ transient studies were conducted. RESULTS Inducible cardiomyocyte-specific loss of Nexn in adult mice resulted in a dilated cardiomyopathy with reduced cardiac function (13% reduction in percentage fractional shortening; P<0.05). In vivo and in vitro analyses of adult mouse heart samples revealed that NEXN was essential for optimal contraction and calcium handling and was required for maintenance of T-tubule network organization (transverse tubular component in Nexn inducible adult cardiomyocyte-specific KO mice reduced by 40% with respect to controls, P<0.05). CONCLUSIONS Results here reported reveal NEXN to be a pivotal component of adult junctional membrane complexes required for maintenance of transverse-axial tubular architecture. These results demonstrate that NEXN plays an essential role in the adult cardiomyocyte and give further understanding of pathological mechanisms responsible for cardiomyopathy in patients carrying mutations in the NEXN gene.
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MESH Headings
- Age Factors
- Animals
- Calcium/metabolism
- Cardiomyopathy, Dilated/genetics
- Cardiomyopathy, Dilated/metabolism
- Cardiomyopathy, Dilated/physiopathology
- Disease Models, Animal
- Mice
- Mice, Knockout
- Microfilament Proteins/genetics
- Microfilament Proteins/metabolism
- Microfilament Proteins/physiology
- Microtubules/metabolism
- Microtubules/physiology
- Myocytes, Cardiac/metabolism
- Myocytes, Cardiac/physiology
- Ventricular Dysfunction, Left/genetics
- Ventricular Dysfunction, Left/metabolism
- Ventricular Dysfunction, Left/physiopathology
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Affiliation(s)
- Simone Spinozzi
- Department of Medicine, University of California San Diego, La Jolla, CA 92093, USA
| | - Canzhao Liu
- Department of Medicine, University of California San Diego, La Jolla, CA 92093, USA
| | - Ze’e Chen
- Department of Medicine, University of California San Diego, La Jolla, CA 92093, USA
| | - Wei Feng
- Department of Medicine, University of California San Diego, La Jolla, CA 92093, USA
| | - Lunfeng Zhang
- Department of Medicine, University of California San Diego, La Jolla, CA 92093, USA
- Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA 92093, USA
| | - Kunfu Ouyang
- Drug Discovery Center, State Key Laboratory of Chemical Oncogenomics, School of Chemical Biology and Biotechnology, Peking University Shenzhen Graduate School, Shenzhen 518055, China
| | - Sylvia M. Evans
- Department of Medicine, University of California San Diego, La Jolla, CA 92093, USA
- Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA 92093, USA
| | - Ju Chen
- Department of Medicine, University of California San Diego, La Jolla, CA 92093, USA
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9
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Silbernagel N, Körner A, Balitzki J, Jaggy M, Bertels S, Richter B, Hippler M, Hellwig A, Hecker M, Bastmeyer M, Ullrich ND. Shaping the heart: Structural and functional maturation of iPSC-cardiomyocytes in 3D-micro-scaffolds. Biomaterials 2020; 227:119551. [DOI: 10.1016/j.biomaterials.2019.119551] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 10/06/2019] [Accepted: 10/14/2019] [Indexed: 02/05/2023]
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10
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Sheard TD, Hurley ME, Colyer J, White E, Norman R, Pervolaraki E, Narayanasamy KK, Hou Y, Kirton HM, Yang Z, Hunter L, Shim JU, Clowsley AH, Smith AJ, Baddeley D, Soeller C, Colman MA, Jayasinghe I. Three-Dimensional and Chemical Mapping of Intracellular Signaling Nanodomains in Health and Disease with Enhanced Expansion Microscopy. ACS NANO 2019; 13:2143-2157. [PMID: 30715853 PMCID: PMC6396323 DOI: 10.1021/acsnano.8b08742] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Accepted: 02/04/2019] [Indexed: 05/08/2023]
Abstract
Nanodomains are intracellular foci which transduce signals between major cellular compartments. One of the most ubiquitous signal transducers, the ryanodine receptor (RyR) calcium channel, is tightly clustered within these nanodomains. Super-resolution microscopy has previously been used to visualize RyR clusters near the cell surface. A majority of nanodomains located deeper within cells have remained unresolved due to limited imaging depths and axial resolution of these modalities. A series of enhancements made to expansion microscopy allowed individual RyRs to be resolved within planar nanodomains at the cell periphery and the curved nanodomains located deeper within the interiors of cardiomyocytes. With a resolution of ∼ 15 nm, we localized both the position of RyRs and their individual phosphorylation for the residue Ser2808. With a three-dimensional imaging protocol, we observed disturbances to the RyR arrays in the nanometer scale which accompanied right-heart failure caused by pulmonary hypertension. The disease coincided with a distinct gradient of RyR hyperphosphorylation from the edge of the nanodomain toward the center, not seen in healthy cells. This spatial profile appeared to contrast distinctly from that sustained by the cells during acute, physiological hyperphosphorylation when they were stimulated with a β-adrenergic agonist. Simulations of RyR arrays based on the experimentally determined channel positions and phosphorylation signatures showed how the nanoscale dispersal of the RyRs during pathology diminishes its intrinsic likelihood to ignite a calcium signal. It also revealed that the natural topography of RyR phosphorylation could offset potential heterogeneity in nanodomain excitability which may arise from such RyR reorganization.
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Affiliation(s)
- Thomas
M. D. Sheard
- School
of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Miriam E. Hurley
- School
of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - John Colyer
- School
of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Ed White
- School
of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Ruth Norman
- School
of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Eleftheria Pervolaraki
- School
of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Kaarjel K. Narayanasamy
- School
of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Yufeng Hou
- Institute
of Experimental Medical Research, Oslo University
Hospital Ullevål, Oslo 0407, Norway
| | - Hannah M. Kirton
- School
of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Zhaokang Yang
- School
of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Liam Hunter
- School
of Physics and Astronomy, Faculty of Mathematics and Physical Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Jung-uk Shim
- School
of Physics and Astronomy, Faculty of Mathematics and Physical Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | | | - Andrew J. Smith
- School
of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - David Baddeley
- Auckland
Bioengineering Institute, University of
Auckland, UniServices
House, Level, 6/70 Symonds St, Grafton, Auckland 1010, New Zealand
| | - Christian Soeller
- Living
Systems Institute, University of Exeter, Devon EX4 4QL, United Kingdom
| | - Michael A. Colman
- School
of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Izzy Jayasinghe
- School
of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
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11
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Hiess F, Detampel P, Nolla-Colomer C, Vallmitjana A, Ganguly A, Amrein M, Ter Keurs HEDJ, Benítez R, Hove-Madsen L, Chen SRW. Dynamic and Irregular Distribution of RyR2 Clusters in the Periphery of Live Ventricular Myocytes. Biophys J 2019; 114:343-354. [PMID: 29401432 DOI: 10.1016/j.bpj.2017.11.026] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Revised: 10/01/2017] [Accepted: 11/03/2017] [Indexed: 10/18/2022] Open
Abstract
Cardiac ryanodine receptors (RyR2s) are Ca2+ release channels clustering in the sarcoplasmic reticulum membrane. These clusters are believed to be the elementary units of Ca2+ release. The distribution of these Ca2+ release units plays a critical role in determining the spatio-temporal profile and stability of sarcoplasmic reticulum Ca2+ release. RyR2 clusters located in the interior of cardiomyocytes are arranged in highly ordered arrays. However, little is known about the distribution and function of RyR2 clusters in the periphery of cardiomyocytes. Here, we used a knock-in mouse model expressing a green fluorescence protein (GFP)-tagged RyR2 to localize RyR2 clusters in live ventricular myocytes by virtue of their GFP fluorescence. Confocal imaging and total internal reflection fluorescence microscopy was employed to determine and compare the distribution of GFP-RyR2 in the interior and periphery of isolated live ventricular myocytes and in intact hearts. We found tightly ordered arrays of GFP-RyR2 clusters in the interior, as previously described. In contrast, irregular distribution of GFP-RyR2 clusters was observed in the periphery. Time-lapse total internal reflection fluorescence imaging revealed dynamic movements of GFP-RyR2 clusters in the periphery, which were affected by external Ca2+ and RyR2 activator (caffeine) and inhibitor (tetracaine), but little detectable movement of GFP-RyR2 clusters in the interior. Furthermore, simultaneous Ca2+- and GFP-imaging demonstrated that peripheral RyR2 clusters with an irregular distribution pattern are functional with a Ca2+ release profile similar to that in the interior. These results indicate that the distribution of RyR2 clusters in the periphery of live ventricular myocytes is irregular and dynamic, which is different from that of RyR2 clusters in the interior.
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Affiliation(s)
- Florian Hiess
- Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada
| | - Pascal Detampel
- Department of Pharmaceutical Sciences, University of Basel, Basel, Switzerland
| | - Carme Nolla-Colomer
- Automatic Control Department, Universitat Politècnica de Catalunya-Barcelona Tech, Barcelona, Spain
| | - Alex Vallmitjana
- Automatic Control Department, Universitat Politècnica de Catalunya-Barcelona Tech, Barcelona, Spain
| | - Anutosh Ganguly
- Department of Microbiology, Immunology and Infectious Diseases, University of Calgary, Calgary, Alberta, Canada
| | - Matthias Amrein
- Department of Biology and Anatomy, University of Calgary, Calgary, Alberta, Canada
| | - Henk E D J Ter Keurs
- Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada
| | - Raul Benítez
- Automatic Control Department, Universitat Politècnica de Catalunya-Barcelona Tech, Barcelona, Spain
| | - Leif Hove-Madsen
- Biomedical Research Institute Barcelona CSIC-IIBB, Sant Pau, Hospital de Sant Pau, Barcelona, Spain
| | - S R Wayne Chen
- Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada.
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12
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Sheard TMD, Kharche SR, Pinali C, Shiels HA. 3D ultrastructural organisation of calcium release units in the avian sarcoplasmic reticulum. J Exp Biol 2019; 222:jeb.197640. [DOI: 10.1242/jeb.197640] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Accepted: 02/22/2019] [Indexed: 11/20/2022]
Abstract
Excitation-contraction coupling in vertebrate hearts is underpinned by calcium (Ca2+) release from Ca2+ release units (CRUs). CRUs are formed by clusters of channels called ryanodine receptors on the sarcoplasmic reticulum (SR) within the cardiomyocyte. Distances between CRUs influence the diffusion of Ca2+, thus influencing the rate and strength of excitation-contraction coupling. Avian myocytes lack T-tubules, thus Ca2+ from surface CRUs (peripheral couplings, PCs), must diffuse to internal CRU sites of the corbular SR (cSR) during centripetal propagation. Despite this, avian hearts achieve higher contractile rates and develop greater contractile strength than many mammalian hearts, which have T-tubules to provide simultaneous activation of the Ca2+ signal through the myocyte. We used 3D electron tomography to test the hypothesis that the intracellular distribution of CRUs in the avian heart permits faster and stronger contractions despite the absence T-tubules. Nearest edge-edge distances between PCs and cSR, and geometric information including surface area and volumes of individual cSR, were obtained for each cardiac chamber of the White Leghorn chicken. Computational modelling was then used to establish a relationship between CRUs distances and cell activation time in the avian heart. Our data suggest that cSR clustered close together along the Z-line is vital for rapid propagation of the Ca2+ signal from the cell periphery to the cell centre which would aid in the strong and fast contractions of the avian heart.
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Affiliation(s)
- Thomas M. D. Sheard
- University of Manchester, Faculty of Biology, Medicine and Health, Oxford Road, Manchester, M13 9PL, UK
| | - Sanjay R. Kharche
- University of Manchester, Faculty of Biology, Medicine and Health, Oxford Road, Manchester, M13 9PL, UK
- Department of Medical Biophysics, University of Western Ontario, London, N6A 3K7, Canada
- Lawson Health Research Institute, 800 Commissioners Road East, London, Ontario, N6C 2R5, Canada
| | - Christian Pinali
- University of Manchester, Faculty of Biology, Medicine and Health, Oxford Road, Manchester, M13 9PL, UK
| | - Holly A. Shiels
- University of Manchester, Faculty of Biology, Medicine and Health, Oxford Road, Manchester, M13 9PL, UK
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13
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Jones PP, MacQuaide N, Louch WE. Dyadic Plasticity in Cardiomyocytes. Front Physiol 2018; 9:1773. [PMID: 30618792 PMCID: PMC6298195 DOI: 10.3389/fphys.2018.01773] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Accepted: 11/23/2018] [Indexed: 11/13/2022] Open
Abstract
Contraction of cardiomyocytes is dependent on sub-cellular structures called dyads, where invaginations of the surface membrane (t-tubules) form functional junctions with the sarcoplasmic reticulum (SR). Within each dyad, Ca2+ entry through t-tubular L-type Ca2+ channels (LTCCs) elicits Ca2+ release from closely apposed Ryanodine Receptors (RyRs) in the SR membrane. The efficiency of this process is dependent on the density and macroscale arrangement of dyads, but also on the nanoscale organization of LTCCs and RyRs within them. We presently review accumulating data demonstrating the remarkable plasticity of these structures. Dyads are known to form gradually during development, with progressive assembly of both t-tubules and junctional SR terminals, and precise trafficking of LTCCs and RyRs. While dyads can exhibit compensatory remodeling when required, dyadic degradation is believed to promote impaired contractility and arrythmogenesis in cardiac disease. Recent data indicate that this plasticity of dyadic structure/function is dependent on the regulatory proteins junctophilin-2, amphiphysin-2 (BIN1), and caveolin-3, which critically arrange dyadic membranes while stabilizing the position and activity of LTCCs and RyRs. Indeed, emerging evidence indicates that clustering of both channels enables "coupled gating", implying that nanoscale localization and function are intimately linked, and may allow fine-tuning of LTCC-RyR crosstalk. We anticipate that improved understanding of dyadic plasticity will provide greater insight into the processes of cardiac compensation and decompensation, and new opportunities to target the basic mechanisms underlying heart disease.
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Affiliation(s)
- Peter P. Jones
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
- HeartOtago, University of Otago, Dunedin, New Zealand
| | - Niall MacQuaide
- Institute of Cardiovascular Sciences, University of Glasgow, Glasgow, United Kingdom
- Clyde Biosciences, Glasgow, United Kingdom
| | - William E. Louch
- Institute for Experimental Medical Research, Oslo University Hospital, University of Oslo, Oslo, Norway
- KG Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
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14
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Jayasinghe I, Clowsley AH, de Langen O, Sali SS, Crossman DJ, Soeller C. Shining New Light on the Structural Determinants of Cardiac Couplon Function: Insights From Ten Years of Nanoscale Microscopy. Front Physiol 2018; 9:1472. [PMID: 30405432 PMCID: PMC6204384 DOI: 10.3389/fphys.2018.01472] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Accepted: 09/28/2018] [Indexed: 12/12/2022] Open
Abstract
Remodelling of the membranes and protein clustering patterns during the pathogenesis of cardiomyopathies has renewed the interest in spatial visualisation of these structures in cardiomyocytes. Coincidental emergence of single molecule (super-resolution) imaging and tomographic electron microscopy tools in the last decade have led to a number of new observations on the structural features of the couplons, the primary sites of excitation-contraction coupling in the heart. In particular, super-resolution and tomographic electron micrographs have revised and refined the classical views of the nanoscale geometries of couplons, t-tubules and the organisation of the principal calcium handling proteins in both healthy and failing hearts. These methods have also allowed the visualisation of some features which were too small to be detected with conventional microscopy tools. With new analytical capabilities such as single-protein mapping, in situ protein quantification, correlative and live cell imaging we are now observing an unprecedented interest in adapting these research tools across the cardiac biophysical research discipline. In this article, we review the depth of the new insights that have been enabled by these tools toward understanding the structure and function of the cardiac couplon. We outline the major challenges that remain in these experiments and emerging avenues of research which will be enabled by these technologies.
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Affiliation(s)
- Izzy Jayasinghe
- Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | | | - Oscar de Langen
- Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Sonali S Sali
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India
| | - David J Crossman
- Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Christian Soeller
- Living Systems Institute, University of Exeter, Exeter, United Kingdom
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15
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Schobesberger S, Wright P, Tokar S, Bhargava A, Mansfield C, Glukhov AV, Poulet C, Buzuk A, Monszpart A, Sikkel M, Harding SE, Nikolaev VO, Lyon AR, Gorelik J. T-tubule remodelling disturbs localized β2-adrenergic signalling in rat ventricular myocytes during the progression of heart failure. Cardiovasc Res 2018; 113:770-782. [PMID: 28505272 PMCID: PMC5437368 DOI: 10.1093/cvr/cvx074] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Accepted: 05/11/2017] [Indexed: 11/12/2022] Open
Abstract
Aims Cardiomyocyte β2-adrenergic receptor (β2AR) cyclic adenosine monophosphate (cAMP) signalling is regulated by the receptors' subcellular location within transverse tubules (T-tubules), via interaction with structural and regulatory proteins, which form a signalosome. In chronic heart failure (HF), β2ARs redistribute from T-tubules to the cell surface, which disrupts functional signalosomes and leads to diffuse cAMP signalling. However, the functional consequences of structural changes upon β2AR-cAMP signalling during progression from hypertrophy to advanced HF are unknown. Methods and results Rat left ventricular myocytes were isolated at 4-, 8-, and 16-week post-myocardial infarction (MI), β2ARs were stimulated either via whole-cell perfusion or locally through the nanopipette of the scanning ion conductance microscope. cAMP release was measured via a Förster Resonance Energy Transfer-based sensor Epac2-camps. Confocal imaging of di-8-ANNEPS-stained cells and immunoblotting were used to determine structural alterations. At 4-week post-MI, T-tubule regularity, density and junctophilin-2 (JPH2) expression were significantly decreased. The amplitude of local β2AR-mediated cAMP in T-tubules was reduced and cAMP diffused throughout the cytosol instead of being locally confined. This was accompanied by partial caveolin-3 (Cav-3) dissociation from the membrane. At 8-week post-MI, the β2AR-mediated cAMP response was observed at the T-tubules and the sarcolemma (crest). Finally, at 16-week post-MI, the whole cell β2AR-mediated cAMP signal was depressed due to adenylate cyclase dysfunction, while overall Cav-3 levels were significantly increased and a substantial portion of Cav-3 dissociated into the cytosol. Overexpression of JPH2 in failing cells in vitro or AAV9.SERCA2a gene therapy in vivo did not improve β2AR-mediated signal compartmentation or reduce cAMP diffusion. Conclusion Although changes in T-tubule structure and β2AR-mediated cAMP signalling are significant even at 4-week post-MI, progression to the HF phenotype is not linear. At 8-week post-MI the loss of β2AR-mediated cAMP is temporarily reversed. Complete disorganization of β2AR-mediated cAMP signalling due to changes in functional receptor localization and cellular structure occurs at 16-week post-MI.
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Affiliation(s)
- Sophie Schobesberger
- Department of Cardiac Medicine, National Heart and Lung Institute, Imperial College, Du Cane Road, London W12 0NN, UK.,Institute of Experimental Cardiovascular Research, University Medical Center Hamburg-Eppendorf, Martinistraße, Hamburg D-20246, Germany
| | - Peter Wright
- Department of Cardiac Medicine, National Heart and Lung Institute, Imperial College, Du Cane Road, London W12?0NN, UK
| | - Sergiy Tokar
- Department of Cardiac Medicine, National Heart and Lung Institute, Imperial College, Du Cane Road, London W12?0NN, UK
| | - Anamika Bhargava
- Department of Cardiac Medicine, National Heart and Lung Institute, Imperial College, Du Cane Road, London W12 0NN, UK.,Department of Biotechnology, Indian Institute of Technology Hyderabad, Ordnance Factory Estate, Yeddumailaram, 502205 Telangana, India
| | - Catherine Mansfield
- Department of Cardiac Medicine, National Heart and Lung Institute, Imperial College, Du Cane Road, London W12?0NN, UK
| | - Alexey V Glukhov
- Department of Cardiac Medicine, National Heart and Lung Institute, Imperial College, Du Cane Road, London W12?0NN, UK
| | - Claire Poulet
- Department of Cardiac Medicine, National Heart and Lung Institute, Imperial College, Du Cane Road, London W12?0NN, UK
| | - Andrey Buzuk
- Department of Cardiac Medicine, National Heart and Lung Institute, Imperial College, Du Cane Road, London W12?0NN, UK
| | - Aron Monszpart
- Department of Computer Science, University College London, Gower Street, London WC1E 6BT, UK
| | - Markus Sikkel
- Department of Cardiac Medicine, National Heart and Lung Institute, Imperial College, Du Cane Road, London W12?0NN, UK
| | - Sian E Harding
- Department of Cardiac Medicine, National Heart and Lung Institute, Imperial College, Du Cane Road, London W12?0NN, UK
| | - Viacheslav O Nikolaev
- Institute of Experimental Cardiovascular Research, University Medical Center Hamburg-Eppendorf, Martinistraße, Hamburg D-20246, Germany
| | - Alexander R Lyon
- Department of Cardiac Medicine, National Heart and Lung Institute, Imperial College, Du Cane Road, London W12 0NN, UK.,NIHR Cardiovascular Biomedical Research Unit, Department of Cardiology, Royal Brompton Hospital, Sydney Street, London SW3 6NP, UK
| | - Julia Gorelik
- Department of Cardiac Medicine, National Heart and Lung Institute, Imperial College, Du Cane Road, London W12?0NN, UK
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16
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Macková K, Zahradníková A, Hoťka M, Hoffmannová B, Zahradník I, Zahradníková A. Calcium release-dependent inactivation precedes formation of the tubular system in developing rat cardiac myocytes. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2017; 46:691-703. [PMID: 28913625 DOI: 10.1007/s00249-017-1249-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 06/21/2017] [Accepted: 08/17/2017] [Indexed: 01/06/2023]
Abstract
Developing cardiac myocytes undergo substantial structural and functional changes transforming the mechanism of excitation-contraction coupling from the embryonic form, based on calcium influx through sarcolemmal DHPR calcium channels, to the adult form, relying on local calcium release through RYR calcium channels of sarcoplasmic reticulum stimulated by calcium influx. We characterized day-by-day the postnatal development of the structure of sarcolemma, using techniques of confocal fluorescence microscopy, and the development of the calcium current, measured by the whole-cell patch-clamp in isolated rat ventricular myocytes. We characterized the appearance and expansion of the t-tubule system and compared it with the appearance and progress of the calcium current inactivation induced by the release of calcium ions from sarcoplasmic reticulum as structural and functional measures of direct DHPR-RYR interaction. The release-dependent inactivation of calcium current preceded the development of the t-tubular system by several days, indicating formation of the first DHPR-RYR couplons at the surface sarcolemma and their later spreading close to contractile myofibrils with the growing t-tubules. Large variability of both of the measured parameters among individual myocytes indicates uneven maturation of myocytes within the growing myocardium.
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Affiliation(s)
- Katarina Macková
- Department of Muscle Cell Research, Institute of Molecular Physiology and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Dúbravská cesta 9, 840 05, Bratislava, Slovakia
| | - Alexandra Zahradníková
- Department of Muscle Cell Research, Institute of Molecular Physiology and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Dúbravská cesta 9, 840 05, Bratislava, Slovakia
| | - Matej Hoťka
- Department of Muscle Cell Research, Institute of Molecular Physiology and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Dúbravská cesta 9, 840 05, Bratislava, Slovakia
| | - Barbora Hoffmannová
- Department of Muscle Cell Research, Institute of Molecular Physiology and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Dúbravská cesta 9, 840 05, Bratislava, Slovakia
| | - Ivan Zahradník
- Department of Muscle Cell Research, Institute of Molecular Physiology and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Dúbravská cesta 9, 840 05, Bratislava, Slovakia
| | - Alexandra Zahradníková
- Department of Muscle Cell Research, Institute of Molecular Physiology and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Dúbravská cesta 9, 840 05, Bratislava, Slovakia.
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17
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Bennett PM, Ehler E, Wilson AJ. Sarcoplasmic reticulum is an intermediary of mitochondrial and myofibrillar growth at the intercalated disc. J Muscle Res Cell Motil 2016; 37:55-69. [PMID: 27329158 PMCID: PMC5010836 DOI: 10.1007/s10974-016-9444-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Accepted: 05/22/2016] [Indexed: 11/30/2022]
Abstract
In cardiomyocytes columns of intermyofibrillar mitochondria run up to the intercalated disc (ID); half are collinear with those in the neighbouring cell, suggesting coordinated addition of sarcomeres and mitochondria both within and between cells during cardiomyocyte growth. Recent evidence for an association between sarcoplasmic reticulum (SR) and mitochondria indicates that the SR may be an intermediary in this coordinated behaviour. For this reason we have investigated the arrangement of SR and t tubules with respect to mitochondria and myofibrils, particularly at the ID. In the body of the cardiomyocyte the mitochondrial columns are frequently intersected by transverse tubules. In addition, we find that a majority of axial tubules are sandwiched between mitochondria and myofibril. No tubules are found at the ID. SR coats mitochondrial columns and fibrils throughout their length and reaches towards the peaks of the ID membrane where it attaches in the form of junctional (j)SR. These peripheral ID couplings are often situated between mitochondria and ID membrane, suggesting an SR connection between the two. In dilated cardiomyopathy (DCM) the mitochondria are somewhat disordered and clumped. In a mouse model for DCM, the muscle LIM protein KO, we find that there is a lack of mitochondria near the ID, suggesting the uncoupling of the myofibril/mitochondria organisation during growth. SR still coats the fibrils and reaches the ID folds in a jSR coupling. Unlike in control tissue, however, loops and long fingers of ID membrane penetrate into the proximal sarcomere suggesting a possible intermediary state in cardiomyocyte growth.
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Affiliation(s)
- Pauline M Bennett
- Randall Division of Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London, SE1 1UL, UK.
| | - Elisabeth Ehler
- Randall Division of Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London, SE1 1UL, UK
| | - Amanda J Wilson
- Randall Division of Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London, SE1 1UL, UK.,Department of Life Sciences, Sir Ernst Chain Building, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK
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18
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Hiess F, Vallmitjana A, Wang R, Cheng H, ter Keurs HEDJ, Chen J, Hove-Madsen L, Benitez R, Chen SRW. Distribution and Function of Cardiac Ryanodine Receptor Clusters in Live Ventricular Myocytes. J Biol Chem 2015; 290:20477-87. [PMID: 26109063 DOI: 10.1074/jbc.m115.650531] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Indexed: 11/06/2022] Open
Abstract
The cardiac Ca(2+) release channel (ryanodine receptor, RyR2) plays an essential role in excitation-contraction coupling in cardiac muscle cells. Effective and stable excitation-contraction coupling critically depends not only on the expression of RyR2, but also on its distribution. Despite its importance, little is known about the distribution and organization of RyR2 in living cells. To study the distribution of RyR2 in living cardiomyocytes, we generated a knock-in mouse model expressing a GFP-tagged RyR2 (GFP-RyR2). Confocal imaging of live ventricular myocytes isolated from the GFP-RyR2 mouse heart revealed clusters of GFP-RyR2 organized in rows with a striated pattern. Similar organization of GFP-RyR2 clusters was observed in fixed ventricular myocytes. Immunofluorescence staining with the anti-α-actinin antibody (a z-line marker) showed that nearly all GFP-RyR2 clusters were localized in the z-line zone. There were small regions with dislocated GFP-RyR2 clusters. Interestingly, these same regions also displayed dislocated z-lines. Staining with di-8-ANEPPS revealed that nearly all GFP-RyR2 clusters were co-localized with transverse but not longitudinal tubules, whereas staining with MitoTracker Red showed that GFP-RyR2 clusters were not co-localized with mitochondria in live ventricular myocytes. We also found GFP-RyR2 clusters interspersed between z-lines only at the periphery of live ventricular myocytes. Simultaneous detection of GFP-RyR2 clusters and Ca(2+) sparks showed that Ca(2+) sparks originated exclusively from RyR2 clusters. Ca(2+) sparks from RyR2 clusters induced no detectable changes in mitochondrial Ca(2+) level. These results reveal, for the first time, the distribution of RyR2 clusters and its functional correlation in living ventricular myocytes.
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Affiliation(s)
- Florian Hiess
- From the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology and
| | - Alexander Vallmitjana
- the Department of Automatic Control, Universitat Politècnica de Catalunya, 08034 Barcelona, Spain
| | - Ruiwu Wang
- From the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology and
| | - Hongqiang Cheng
- the Department of Medicine, University of California at San Diego, La Jolla, California 92161, and
| | - Henk E D J ter Keurs
- the Libin Cardiovascular Institute of Alberta, Department of Cardiac Sciences, University of Calgary, Calgary, Alberta T2N 1N4, Canada
| | - Ju Chen
- the Department of Medicine, University of California at San Diego, La Jolla, California 92161, and
| | - Leif Hove-Madsen
- the Cardiovascular Research Centre CSIC-ICCC, Hospital de Sant Pau, 08025 Barcelona, Spain
| | - Raul Benitez
- the Department of Automatic Control, Universitat Politècnica de Catalunya, 08034 Barcelona, Spain
| | - S R Wayne Chen
- From the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology and
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19
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Walweel K, Laver DR. Mechanisms of SR calcium release in healthy and failing human hearts. Biophys Rev 2015; 7:33-41. [PMID: 28509976 PMCID: PMC5425750 DOI: 10.1007/s12551-014-0152-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Accepted: 11/25/2014] [Indexed: 01/08/2023] Open
Abstract
Normal heart contraction and rhythm relies on the proper flow of calcium ions (Ca2+) into cardiac cells and between their intracellular organelles, and any disruption can lead to arrhythmia and sudden cardiac death. Electrical excitation of the surface membrane activates voltage-dependent L-type Ca2+ channels to open and allow Ca2+ to enter the cytoplasm. The subsequent increase in cytoplasmic Ca2+ concentration activates calcium release channels (RyR2) located at specialised Ca2+ release sites in the sarcoplasmic reticulum (SR), which serves as an intracellular Ca2+ store. Animal models have provided valuable insights into how intracellular Ca2+ transport mechanisms are altered in human heart failure. The aim of this review is to examine how Ca2+ release sites are remodelled in heart failure and how this affects intracellular Ca2+ transport with an emphasis on Ca2+ release mechanisms in the SR. Current knowledge on how heart failure alters the regulation of RyR2 by Ca2+ and Mg2+ and how these mechanisms control the activity of RyR2 in the confines of the Ca2+ release sites is reviewed.
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Affiliation(s)
- K Walweel
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, NSW, 2308, Australia
| | - D R Laver
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, NSW, 2308, Australia.
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20
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Transitions of protein traffic from cardiac ER to junctional SR. J Mol Cell Cardiol 2015; 81:34-45. [PMID: 25640161 DOI: 10.1016/j.yjmcc.2014.12.025] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Revised: 12/29/2014] [Accepted: 12/29/2014] [Indexed: 11/20/2022]
Abstract
The junctional sarcoplasmic reticulum (jSR) is an important and unique ER subdomain in the adult myocyte that concentrates resident proteins to regulate Ca(2+) release. To investigate cellular mechanisms for sorting and trafficking proteins to jSR, we overexpressed canine forms of junctin (JCT) or triadin (TRD) in adult rat cardiomyocytes. Protein accumulation over time was visualized by confocal fluorescence microscopy using species-specific antibodies. Newly synthesized JCTdog and TRDdog appeared by 12-24h as bright fluorescent puncta close to the nuclear surface, decreasing in intensity with increasing radial distance. With increasing time (24-48h), fluorescent puncta appeared at further radial distances from the nuclear surface, eventually populating jSR similar to steady-state patterns. CSQ2-DsRed, a form of CSQ that polymerizes ectopically in rough ER, prevented anterograde traffic of newly made TRDdog and JCTdog, demonstrating common pathways of intracellular trafficking as well as in situ binding to CSQ2 in juxtanuclear rough ER. Reversal of CSQ-DsRed interactions occurred when a form of TRDdog was used in which CSQ2-binding sites are removed ((del)TRD). With increasing levels of expression, CSQ2-DsRed revealed a novel smooth ER network that surrounds nuclei and connects the nuclear axis. TRDdog was retained in smooth ER by binding to CSQ2-DsRed, but escaped to populate jSR puncta. TRDdog and (del)TRD were therefore able to elucidate areas of ER-SR transition. High levels of CSQ2-DsRed in the ER led to loss of jSR puncta labeling, suggesting a plasticity of ER-SR transition sites. We propose a model of ER and SR protein traffic along microtubules, with prominent transverse/radial ER trafficking of JCT and TRD along Z-lines to populate jSR, and an abundant longitudinal/axial smooth ER between and encircling myonuclei, from which jSR proteins traffic.
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21
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Jayasinghe ID, Clowsley AH, Munro M, Hou Y, Crossman DJ, Soeller C. Revealing T-Tubules in Striated Muscle with New Optical Super-Resolution Microscopy Techniquess. Eur J Transl Myol 2014; 25:4747. [PMID: 26913143 PMCID: PMC4748971 DOI: 10.4081/ejtm.2015.4747] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Accepted: 12/18/2014] [Indexed: 01/03/2023] Open
Abstract
The t-tubular system plays a central role in the synchronisation of calcium signalling and excitation-contraction coupling in most striated muscle cells. Light microscopy has been used for imaging t-tubules for well over 100 years and together with electron microscopy (EM), has revealed the three-dimensional complexities of the t-system topology within cardiomyocytes and skeletal muscle fibres from a range of species. The emerging super-resolution single molecule localisation microscopy (SMLM) techniques are offering a near 10-fold improvement over the resolution of conventional fluorescence light microscopy methods, with the ability to spectrally resolve nanometre scale distributions of multiple molecular targets. In conjunction with the next generation of electron microscopy, SMLM has allowed the visualisation and quantification of intricate t-tubule morphologies within large areas of muscle cells at an unprecedented level of detail. In this paper, we review recent advancements in the t-tubule structural biology with the utility of various microscopy techniques. We outline the technical considerations in adapting SMLM to study t-tubules and its potential to further our understanding of the molecular processes that underlie the sub-micron scale structural alterations observed in a range of muscle pathologies.
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Affiliation(s)
| | | | - Michelle Munro
- Department of Physiology, The University of Auckland , New Zealand
| | - Yufeng Hou
- Department of Physiology, The University of Auckland , New Zealand
| | - David J Crossman
- Department of Physiology, The University of Auckland , New Zealand
| | - Christian Soeller
- Biomedical Physics, University of Exeter, UK, New Zealand; Biomedical Physics, University of Exeter, UK, New Zealand
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22
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Caldwell JL, Smith CER, Taylor RF, Kitmitto A, Eisner DA, Dibb KM, Trafford AW. Dependence of cardiac transverse tubules on the BAR domain protein amphiphysin II (BIN-1). Circ Res 2014; 115:986-96. [PMID: 25332206 DOI: 10.1161/circresaha.116.303448] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE Transverse tubules (t-tubules) regulate cardiac excitation-contraction coupling and exhibit interchamber and interspecies differences in expression. In cardiac disease, t-tubule loss occurs and affects the systolic calcium transient. However, the mechanisms controlling t-tubule maintenance and whether these factors differ between species, cardiac chambers, and in a disease setting remain unclear. OBJECTIVE To determine the role of the Bin/Amphiphysin/Rvs domain protein amphiphysin II (AmpII) in regulating t-tubule maintenance and the systolic calcium transient. METHODS AND RESULTS T-tubule density was assessed by di-4-ANEPPS, FM4-64 or WGA staining using confocal microscopy. In rat, ferret, and sheep hearts t-tubule density and AmpII protein levels were lower in the atrium than in the ventricle. Heart failure (HF) was induced in sheep using right ventricular tachypacing and ferrets by ascending aortic coarctation. In both HF models, AmpII protein and t-tubule density were decreased in the ventricles. In the sheep, atrial t-tubules were also lost in HF and AmpII levels decreased. Conversely, junctophilin 2 levels did not show interchamber differences in the rat and ferret nor did they change in HF in the sheep or ferret. In addition, in rat atrial and sheep HF atrial cells where t-tubules were absent, junctophilin 2 had sarcomeric intracellular distribution. Small interfering RNA-induced knockdown of AmpII protein reduced t-tubule density, calcium transient amplitude, and the synchrony of the systolic calcium transient. CONCLUSIONS AmpII is intricately involved in t-tubule maintenance. Reducing AmpII protein decreases t-tubule density, reduces the amplitude, and increases the heterogeneity of the systolic calcium transient.
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Affiliation(s)
- Jessica L Caldwell
- From the Unit of Cardiac Physiology and Cardiac Biophysics Group, Institute of Cardiovascular Sciences, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
| | - Charlotte E R Smith
- From the Unit of Cardiac Physiology and Cardiac Biophysics Group, Institute of Cardiovascular Sciences, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
| | - Rebecca F Taylor
- From the Unit of Cardiac Physiology and Cardiac Biophysics Group, Institute of Cardiovascular Sciences, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
| | - Ashraf Kitmitto
- From the Unit of Cardiac Physiology and Cardiac Biophysics Group, Institute of Cardiovascular Sciences, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
| | - David A Eisner
- From the Unit of Cardiac Physiology and Cardiac Biophysics Group, Institute of Cardiovascular Sciences, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
| | - Katharine M Dibb
- From the Unit of Cardiac Physiology and Cardiac Biophysics Group, Institute of Cardiovascular Sciences, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
| | - Andrew W Trafford
- From the Unit of Cardiac Physiology and Cardiac Biophysics Group, Institute of Cardiovascular Sciences, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom.
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Crocini C, Coppini R, Ferrantini C, Pavone FS, Sacconi L. Functional cardiac imaging by random access microscopy. Front Physiol 2014; 5:403. [PMID: 25368580 PMCID: PMC4202699 DOI: 10.3389/fphys.2014.00403] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Accepted: 09/29/2014] [Indexed: 11/22/2022] Open
Abstract
Advances in the development of voltage sensitive dyes and Ca2+ sensors in combination with innovative microscopy techniques allowed researchers to perform functional measurements with an unprecedented spatial and temporal resolution. At the moment, one of the shortcomings of available technologies is their incapability of imaging multiple fast phenomena while controlling the biological determinants involved. In the near future, ultrafast deflectors can be used to rapidly scan laser beams across the sample, performing optical measurements of action potential and Ca2+ release from multiple sites within cardiac cells and tissues. The same scanning modality could also be used to control local Ca2+ release and membrane electrical activity by activation of caged compounds and light-gated ion channels. With this approach, local Ca2+ or voltage perturbations could be induced, simulating arrhythmogenic events, and their impact on physiological cell activity could be explored. The development of this optical methodology will provide fundamental insights in cardiac disease, boosting new therapeutic strategies, and, more generally, it will represent a new approach for the investigation of the physiology of excitable cells.
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Affiliation(s)
- Claudia Crocini
- European Laboratory for Non-Linear Spectroscopy (LENS) Florence, Italy
| | - Raffaele Coppini
- Division of Pharmacology, Department "NeuroFarBa," University of Florence Florence, Italy
| | - Cecilia Ferrantini
- Division of Physiology, Department of Experimental and Clinical Medicine, University of Florence Florence, Italy
| | - Francesco S Pavone
- European Laboratory for Non-Linear Spectroscopy (LENS) Florence, Italy ; Department of Physics and Astronomy, University of Florence Sesto Fiorentino, Italy ; National Research Council, National Institute of Optics Florence, Italy
| | - Leonardo Sacconi
- European Laboratory for Non-Linear Spectroscopy (LENS) Florence, Italy ; National Research Council, National Institute of Optics Florence, Italy
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24
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Wagner E, Brandenburg S, Kohl T, Lehnart SE. Analysis of tubular membrane networks in cardiac myocytes from atria and ventricles. J Vis Exp 2014:e51823. [PMID: 25350293 PMCID: PMC4541455 DOI: 10.3791/51823] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
In cardiac myocytes a complex network of membrane tubules - the transverse-axial tubule system (TATS) - controls deep intracellular signaling functions. While the outer surface membrane and associated TATS membrane components appear to be continuous, there are substantial differences in lipid and protein content. In ventricular myocytes (VMs), certain TATS components are highly abundant contributing to rectilinear tubule networks and regular branching 3D architectures. It is thought that peripheral TATS components propagate action potentials from the cell surface to thousands of remote intracellular sarcoendoplasmic reticulum (SER) membrane contact domains, thereby activating intracellular Ca2+ release units (CRUs). In contrast to VMs, the organization and functional role of TATS membranes in atrial myocytes (AMs) is significantly different and much less understood. Taken together, quantitative structural characterization of TATS membrane networks in healthy and diseased myocytes is an essential prerequisite towards better understanding of functional plasticity and pathophysiological reorganization. Here, we present a strategic combination of protocols for direct quantitative analysis of TATS membrane networks in living VMs and AMs. For this, we accompany primary cell isolations of mouse VMs and/or AMs with critical quality control steps and direct membrane staining protocols for fluorescence imaging of TATS membranes. Using an optimized workflow for confocal or superresolution TATS image processing, binarized and skeletonized data are generated for quantitative analysis of the TATS network and its components. Unlike previously published indirect regional aggregate image analysis strategies, our protocols enable direct characterization of specific components and derive complex physiological properties of TATS membrane networks in living myocytes with high throughput and open access software tools. In summary, the combined protocol strategy can be readily applied for quantitative TATS network studies during physiological myocyte adaptation or disease changes, comparison of different cardiac or skeletal muscle cell types, phenotyping of transgenic models, and pharmacological or therapeutic interventions.
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Affiliation(s)
- Eva Wagner
- Heart Research Center Goettingen; Clinic of Cardiology & Pulmonology, University Medical Center Goettingen; German Center for Cardiovascular Research (DZHK) partner site Goettingen
| | - Sören Brandenburg
- Heart Research Center Goettingen; Clinic of Cardiology & Pulmonology, University Medical Center Goettingen
| | - Tobias Kohl
- Heart Research Center Goettingen; Clinic of Cardiology & Pulmonology, University Medical Center Goettingen
| | - Stephan E Lehnart
- Heart Research Center Goettingen; Clinic of Cardiology & Pulmonology, University Medical Center Goettingen; German Center for Cardiovascular Research (DZHK) partner site Goettingen; BioMET, Center for Biomedical Engineering & Technology, University of Maryland School of Medicine;
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25
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Asghari P, Scriven DRL, Sanatani S, Gandhi SK, Campbell AIM, Moore EDW. Nonuniform and variable arrangements of ryanodine receptors within mammalian ventricular couplons. Circ Res 2014; 115:252-62. [PMID: 24786399 DOI: 10.1161/circresaha.115.303897] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE Single-tilt tomograms of the dyads in rat ventricular myocytes indicated that type 2 ryanodine receptors (RYR2s) were not positioned in a well-ordered array. Furthermore, the orientation and packing strategy of purified type 1 ryanodine receptors in lipid bilayers is determined by the free Mg2+ concentration. These observations led us to test the hypothesis that RYR2s within the mammalian dyad have multiple and complex arrangements. OBJECTIVES To determine the arrangement of RYR2 tetramers in the dyads of mammalian cardiomyocytes and the effects of physiologically and pathologically relevant factors on this arrangement. METHODS AND RESULTS We used dual-tilt electron tomography to produce en-face views of dyads, enabling a direct examination of RYR2 distribution and arrangement. Rat hearts fixed in situ; isolated rat cardiomyocytes permeabilized, incubated with 1 mmol/L Mg2+, and then fixed; and sections of human ventricle, all showed that the tetramer packing within a dyad was nonuniform containing a mix of checkerboard and side-by-side arrangements, as well as isolated tetramers. Both phosphorylation and 0.1 mmol/L Mg2+ moved the tetramers into a predominantly checkerboard configuration, whereas the 4 mmol/L Mg2+ induced a dense side-by-side arrangement. These changes occurred within 10 minutes of application of the stimuli. CONCLUSIONS The arrangement of RYR2 tetramers within the mammalian dyad is neither uniform nor static. We hypothesize that this is characteristic of the dyad in vivo and may provide a mechanism for modulating the open probabilities of the individual tetramers.
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Affiliation(s)
- Parisa Asghari
- From the Department of Cellular and Physiological Sciences (P.A., D.R.L.S., E.D.W.M.), Department of Pediatrics (S.S.), and Department of Surgery (S.K.G., A.I.M.C.), University of British Columbia, Vancouver, British Columbia, Canada
| | - David R L Scriven
- From the Department of Cellular and Physiological Sciences (P.A., D.R.L.S., E.D.W.M.), Department of Pediatrics (S.S.), and Department of Surgery (S.K.G., A.I.M.C.), University of British Columbia, Vancouver, British Columbia, Canada
| | - Shubhayan Sanatani
- From the Department of Cellular and Physiological Sciences (P.A., D.R.L.S., E.D.W.M.), Department of Pediatrics (S.S.), and Department of Surgery (S.K.G., A.I.M.C.), University of British Columbia, Vancouver, British Columbia, Canada
| | - Sanjiv K Gandhi
- From the Department of Cellular and Physiological Sciences (P.A., D.R.L.S., E.D.W.M.), Department of Pediatrics (S.S.), and Department of Surgery (S.K.G., A.I.M.C.), University of British Columbia, Vancouver, British Columbia, Canada
| | - Andrew I M Campbell
- From the Department of Cellular and Physiological Sciences (P.A., D.R.L.S., E.D.W.M.), Department of Pediatrics (S.S.), and Department of Surgery (S.K.G., A.I.M.C.), University of British Columbia, Vancouver, British Columbia, Canada
| | - Edwin D W Moore
- From the Department of Cellular and Physiological Sciences (P.A., D.R.L.S., E.D.W.M.), Department of Pediatrics (S.S.), and Department of Surgery (S.K.G., A.I.M.C.), University of British Columbia, Vancouver, British Columbia, Canada.
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26
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Ferrantini C, Crocini C, Coppini R, Vanzi F, Tesi C, Cerbai E, Poggesi C, Pavone FS, Sacconi L. The transverse-axial tubular system of cardiomyocytes. Cell Mol Life Sci 2013; 70:4695-710. [PMID: 23846763 PMCID: PMC11113601 DOI: 10.1007/s00018-013-1410-5] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Revised: 06/03/2013] [Accepted: 06/13/2013] [Indexed: 10/26/2022]
Abstract
A characteristic histological feature of striated muscle cells is the presence of deep invaginations of the plasma membrane (sarcolemma), most commonly referred to as T-tubules or the transverse-axial tubular system (TATS). TATS mediates the rapid spread of the electrical signal (action potential) to the cell core triggering Ca(2+) release from the sarcoplasmic reticulum, ultimately inducing myofilament contraction (excitation-contraction coupling). T-tubules, first described in vertebrate skeletal muscle cells, have also been recognized for a long time in mammalian cardiac ventricular myocytes, with a structure and a function that in recent years have been shown to be far more complex and pivotal for cardiac function than initially thought. Renewed interest in T-tubule function stems from the loss and disorganization of T-tubules found in a number of pathological conditions including human heart failure (HF) and dilated and hypertrophic cardiomyopathies, as well as in animal models of HF, chronic ischemia and atrial fibrillation. Disease-related remodeling of the TATS leads to asynchronous and inhomogeneous Ca(2+)-release, due to the presence of orphan ryanodine receptors that have lost their coupling with the dihydropyridine receptors and are either not activated or activated with a delay. Here, we review the physiology of the TATS, focusing first on the relationship between function and structure, and then describing T-tubular remodeling and its reversal in disease settings and following effective therapeutic approaches.
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Affiliation(s)
- C. Ferrantini
- Division of Physiology, Department of Clinical and Experimental Medicine, University of Florence, Florence, Italy
- Centre of Molecular Medicine (C.I.M.M.B.A.), University of Florence, Florence, Italy
| | - C. Crocini
- European Laboratory for Non-Linear Spectroscopy (LENS), University of Florence, Sesto Fiorentino, Italy
| | - R. Coppini
- Centre of Molecular Medicine (C.I.M.M.B.A.), University of Florence, Florence, Italy
- Division of Pharmacology, Department “NeuroFarBa”, University of Florence, Florence, Italy
| | - F. Vanzi
- European Laboratory for Non-Linear Spectroscopy (LENS), University of Florence, Sesto Fiorentino, Italy
- Department of Biology, University of Florence, Florence, Italy
| | - C. Tesi
- Division of Physiology, Department of Clinical and Experimental Medicine, University of Florence, Florence, Italy
- Centre of Molecular Medicine (C.I.M.M.B.A.), University of Florence, Florence, Italy
| | - E. Cerbai
- Centre of Molecular Medicine (C.I.M.M.B.A.), University of Florence, Florence, Italy
- Division of Pharmacology, Department “NeuroFarBa”, University of Florence, Florence, Italy
| | - C. Poggesi
- Division of Physiology, Department of Clinical and Experimental Medicine, University of Florence, Florence, Italy
- Centre of Molecular Medicine (C.I.M.M.B.A.), University of Florence, Florence, Italy
| | - F. S. Pavone
- European Laboratory for Non-Linear Spectroscopy (LENS), University of Florence, Sesto Fiorentino, Italy
- Department of Physics and Astronomy, University of Florence, Sesto Fiorentino, Italy
- National Institute of Optics (INO), National Research Council (CNR), Florence, Italy
| | - L. Sacconi
- European Laboratory for Non-Linear Spectroscopy (LENS), University of Florence, Sesto Fiorentino, Italy
- National Institute of Optics (INO), National Research Council (CNR), Florence, Italy
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27
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Santiago DJ, Ríos E, Shannon TR. Isoproterenol increases the fraction of spark-dependent RyR-mediated leak in ventricular myocytes. Biophys J 2013; 104:976-85. [PMID: 23473480 DOI: 10.1016/j.bpj.2013.01.026] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Revised: 12/21/2012] [Accepted: 01/17/2013] [Indexed: 10/27/2022] Open
Abstract
Recent research suggests that the diastolic ryanodine-receptor-mediated release of Ca(2+) (J(leak)) from the sarcoplasmic reticulum of ventricular myocytes occurs in spark and nonspark forms. Further information about the role(s) of these release manifestations is scarce, however. This study addresses whether the fraction of spark-mediated J(leak) increases due to β-adrenergic stimulation. Confocal microscopy was used to simultaneously image Ca(2+) sparks and quantify J(leak) in intact rabbit myocytes, either in the absence or in the presence of 125 nM isoproterenol. It was found that isoproterenol treatment shifts the spark-frequency-J(leak) relationship toward an increased sensitivity to a [Ca(2+)] trigger. In agreement, a small but significant increase in spark width was found for cells with matched baseline [Ca(2+)] and total SR [Ca(2+)]. The reconstruction of release fluxes, when applied to the average sparks from those selected cells, yielded a wider release source in the isoproterenol event, indicating the recruitment of peripheral ryanodine receptors. Overall, the results presented here indicate that β-adrenergic stimulation increases the spark-dependent fraction of J(leak). Working together, the increased Ca(2+) sensitivity and the greater spark width found during isoproterenol treatment may increase the probability of Ca(2+) wave generation.
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Affiliation(s)
- Demetrio J Santiago
- Department of Molecular Biophysics & Physiology, Rush University, Chicago, Illinois, USA
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28
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Dibb KM, Clarke JD, Eisner DA, Richards MA, Trafford AW. A functional role for transverse (t-) tubules in the atria. J Mol Cell Cardiol 2013; 58:84-91. [PMID: 23147188 DOI: 10.1016/j.yjmcc.2012.11.001] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Accepted: 11/01/2012] [Indexed: 11/17/2022]
Abstract
Mammalian ventricular myocytes are characterised by the presence of an extensive transverse (t-) tubule network which is responsible for the synchronous rise of intracellular Ca(2+) concentration ([Ca(2+)]i) during systole. Disruption to the ventricular t-tubule network occurs in various cardiac pathologies and leads to heterogeneous changes of [Ca(2+)]i which are thought to contribute to the reduced contractility and increased susceptibility to arrhythmias of the diseased ventricle. Here we review evidence that, despite the long-held dogma of atrial cells having no or very few t-tubules, there is indeed an extensive and functionally significant t-tubule network present in atrial myocytes of large mammals including human. Moreover, the atrial t-tubule network is highly plastic in nature and undergoes far more extensive remodelling in heart disease than is the case in the ventricle with profound consequences for the resulting systolic Ca(2+) transient. In addition to considering the functional role of the t-tubule network in the healthy and diseased atria we also provide an overview of recent data concerning the putative factors controlling the formation of t-tubules and conclude by posing some important questions that currently remain to be addressed and whether or not targeting t-tubules offers potential novel therapeutic possibilities for heart disease.
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Affiliation(s)
- Katharine M Dibb
- Institute of Cardiovascular Sciences, Manchester Academic Health Science Centre, 3.08 Core Technology Facility, 46 Grafton Street, Manchester, M13 9PT, UK
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29
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Ca2+ channel and Na+/Ca2+ exchange localization in cardiac myocytes. J Mol Cell Cardiol 2013; 58:22-31. [DOI: 10.1016/j.yjmcc.2012.11.022] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Revised: 11/20/2012] [Accepted: 11/28/2012] [Indexed: 01/01/2023]
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30
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Affiliation(s)
- Tobias Kohl
- Heart Research Center Goettingen, Niedersachsen, Germany
- Department of Cardiology and Pulmonology, University Medical Center Goettingen, Robert-Koch-Str. 40, 37075 Göttingen, Niedersachsen, Germany
| | - Stephan E. Lehnart
- Heart Research Center Goettingen, Niedersachsen, Germany
- Department of Cardiology and Pulmonology, University Medical Center Goettingen, Robert-Koch-Str. 40, 37075 Göttingen, Niedersachsen, Germany
- DZHK (German Centre for Cardiovascular Research) site Goettingen, Germany
- BioMET, Center for Biomedical Engineering and Technology, University of Maryland, Baltimore, MD, USA
- Corresponding author. Tel: +49 551 39 10575; fax: +49 551 39 10650.
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32
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Das T, Hoshijima M. Adding a new dimension to cardiac nano-architecture using electron microscopy: coupling membrane excitation to calcium signaling. J Mol Cell Cardiol 2012. [PMID: 23201225 DOI: 10.1016/j.yjmcc.2012.11.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Advances in microscopic imaging technologies and associated computational methods now allow descriptions of cellular anatomy to go beyond 2-dimensions, revealing new micro-domain dynamics at unprecedented resolutions. In cardiomyocytes, electron microscopy (EM) first described junctional membrane complexes between the sarcolemma and sarcoplasmic reticulum over a half-century ago. Since then, 3-dimensional EM technologies such as electron tomography have become successful in determining the realistic nano-geometry of membrane junctions (dyads and peripheral junctions) and associated structures such as transverse tubules (T-tubules, aka. T-system). Concomitantly, super-resolution light microscopy has gone beyond the diffraction-limit to determine the distribution of molecules, such as ryanodine receptors, with 10(-8) meter (10nm) order accuracy. This review provides the current structural perspective and functional interpretation of membrane junction complexes, which are the central machinery controlling cardiac excitation-contraction coupling via calcium signaling.
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Affiliation(s)
- Tapaswini Das
- The Center for Research in Biological Systems, University of California San Diego, La Jolla, CA 92093, USA
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33
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Super-resolution imaging of EC coupling protein distribution in the heart. J Mol Cell Cardiol 2012; 58:32-40. [PMID: 23159441 DOI: 10.1016/j.yjmcc.2012.11.004] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Revised: 11/05/2012] [Accepted: 11/05/2012] [Indexed: 11/20/2022]
Abstract
The cardiac ryanodine receptor (RyR) plays a central role in the control of contractile function of the heart. In cardiac ventricular myocytes RyRs and associated Ca(2+) handling proteins, including membrane Ca(2+) channels, Ca(2+) pumps and other sarcolemmal and sarcoplasmic reticulum proteins interact to set the time course and amplitude of the electrically triggered cytosolic Ca(2+) transient. It has become increasingly clear that protein distribution and clustering on the nanometer scale is critical in determining the interaction of these proteins and the resulting properties of cardiac Ca(2+) handling. Such intricate near-molecular scale detail cannot be visualized with conventional fluorescence microscopy techniques (e.g. confocal microscopy) but it has recently become accessible with optical super-resolution techniques. These techniques retain the advantages of fluorescent marker technology, i.e. high specificity and excellent contrast, but have a spatial resolution approaching 10nm, i.e. objects not much further apart than 10nm can be distinguished, previously only attainable with electron microscopy. We review the use of these novel imaging techniques for the study of protein distribution in cardiac ventricular myocytes and discuss technical considerations as well as recent findings using super-resolution imaging. An emphasis is on single molecule localization based super-resolution approaches and their use to reveal the complexity of RyR cluster morphology, placement and relationship to other excitation-contraction coupling proteins. Super-resolution imaging approaches have already demonstrated their utility for the study of cardiac structure-function relationships and we anticipate that their use will rapidly increase and help improve our understanding of cardiac Ca(2+) regulation.
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34
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McNary TG, Spitzer KW, Holloway H, Bridge JHB, Kohl P, Sachse FB. Mechanical modulation of the transverse tubular system of ventricular cardiomyocytes. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2012; 110:218-25. [PMID: 22884710 DOI: 10.1016/j.pbiomolbio.2012.07.010] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Accepted: 07/24/2012] [Indexed: 11/19/2022]
Abstract
In most mammalian cardiomyocytes, the transverse tubular system (t-system) is a major site for electrical signaling and excitation-contraction coupling. The t-system consists of membrane invaginations, which are decorated with various proteins involved in excitation-contraction coupling and mechano-electric feedback. Remodeling of the t-system has been reported for cells in culture and various types of heart disease. In this paper, we provide insights into effects of mechanical strain on the t-system in rabbit left ventricular myocytes. Based on fluorescent labeling, three-dimensional scanning confocal microscopy, and digital image analysis, we studied living and fixed isolated cells in different strain conditions. We extracted geometric features of transverse tubules (t-tubules) and characterized their arrangement with respect to the Z-disk. In addition, we studied the t-system in cells from hearts fixed either at zero left ventricular pressure (slack), at 30 mmHg (volume overload), or during lithium-induced contracture, using transmission electron microscopy. Two-dimensional image analysis was used to extract features of t-tubule cross-sections. Our analyses of confocal microscopic images showed that contracture at the cellular level causes deformation of the t-system, increasing the length and volume of t-tubules, and altering their cross-sectional shape. TEM data reconfirmed the presence of mechanically induced changes in t-tubular cross sections. In summary, our studies suggest that passive longitudinal stretching and active contraction of ventricular cardiomyocytes affect the geometry of t-tubules. This confirms that mechanical changes at cellular levels could promote alterations in partial volumes that would support a convection-assisted mode of exchange between the t-system content and extracellular space.
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Affiliation(s)
- Thomas G McNary
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, 95 South 2000 East, Salt Lake City, UT 84112-5000, USA.
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35
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Wagner E, Lauterbach MA, Kohl T, Westphal V, Williams GSB, Steinbrecher JH, Streich JH, Korff B, Tuan HTM, Hagen B, Luther S, Hasenfuss G, Parlitz U, Jafri MS, Hell SW, Lederer WJ, Lehnart SE. Stimulated emission depletion live-cell super-resolution imaging shows proliferative remodeling of T-tubule membrane structures after myocardial infarction. Circ Res 2012; 111:402-14. [PMID: 22723297 DOI: 10.1161/circresaha.112.274530] [Citation(s) in RCA: 143] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE Transverse tubules (TTs) couple electric surface signals to remote intracellular Ca(2+) release units (CRUs). Diffraction-limited imaging studies have proposed loss of TT components as disease mechanism in heart failure (HF). OBJECTIVES Objectives were to develop quantitative super-resolution strategies for live-cell imaging of TT membranes in intact cardiomyocytes and to show that TT structures are progressively remodeled during HF development, causing early CRU dysfunction. METHODS AND RESULTS Using stimulated emission depletion (STED) microscopy, we characterized individual TTs with nanometric resolution as direct readout of local membrane morphology 4 and 8 weeks after myocardial infarction (4pMI and 8pMI). Both individual and network TT properties were investigated by quantitative image analysis. The mean area of TT cross sections increased progressively from 4pMI to 8pMI. Unexpectedly, intact TT networks showed differential changes. Longitudinal and oblique TTs were significantly increased at 4pMI, whereas transversal components appeared decreased. Expression of TT-associated proteins junctophilin-2 and caveolin-3 was significantly changed, correlating with network component remodeling. Computational modeling of spatial changes in HF through heterogeneous TT reorganization and RyR2 orphaning (5000 of 20 000 CRUs) uncovered a local mechanism of delayed subcellular Ca(2+) release and action potential prolongation. CONCLUSIONS This study introduces STED nanoscopy for live mapping of TT membrane structures. During early HF development, the local TT morphology and associated proteins were significantly altered, leading to differential network remodeling and Ca(2+) release dyssynchrony. Our data suggest that TT remodeling during HF development involves proliferative membrane changes, early excitation-contraction uncoupling, and network fracturing.
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Affiliation(s)
- Eva Wagner
- Heart Research Center Goettingen, University Medicine Goettingen, Goettingen, Germany
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Hake J, Edwards AG, Yu Z, Kekenes-Huskey PM, Michailova AP, McCammon JA, Holst MJ, Hoshijima M, McCulloch AD. Modelling cardiac calcium sparks in a three-dimensional reconstruction of a calcium release unit. J Physiol 2012; 590:4403-22. [PMID: 22495592 DOI: 10.1113/jphysiol.2012.227926] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Triggered release of Ca2+ from an individual sarcoplasmic reticulum (SR) Ca(2+) release unit (CRU) is the fundamental event of cardiac excitation–contraction coupling, and spontaneous release events (sparks) are the major contributor to diastolic Ca(2+) leak in cardiomyocytes. Previous model studies have predicted that the duration and magnitude of the spark is determined by the local CRU geometry, as well as the localization and density of Ca(2+) handling proteins. We have created a detailed computational model of a CRU, and developed novel tools to generate the computational geometry from electron tomographic images. Ca(2+) diffusion was modelled within the SR and the cytosol to examine the effects of localization and density of the Na(+)/Ca(2+) exchanger, sarco/endoplasmic reticulum Ca(2+)-ATPase 2 (SERCA), and calsequestrin on spark dynamics. We reconcile previous model predictions of approximately 90% local Ca(2+) depletion in junctional SR, with experimental reports of about 40%. This analysis supports the hypothesis that dye kinetics and optical averaging effects can have a significant impact on measures of spark dynamics. Our model also predicts that distributing calsequestrin within non-junctional Z-disc SR compartments, in addition to the junctional compartment, prolongs spark release time as reported by Fluo5. By pumping Ca(2+) back into the SR during a release, SERCA is able to prolong a Ca(2+) spark, and this may contribute to SERCA-dependent changes in Ca(2+) wave speed. Finally, we show that including the Na(+)/Ca(2+) exchanger inside the dyadic cleft does not alter local [Ca(2+)] during a spark.
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Affiliation(s)
- Johan Hake
- Department of Bioengineering, University of California San Diego, CA, USA.
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Asghari P, Scriven DRL, Hoskins J, Fameli N, van Breemen C, Moore EDW. The structure and functioning of the couplon in the mammalian cardiomyocyte. PROTOPLASMA 2012; 249 Suppl 1:S31-S38. [PMID: 22057630 DOI: 10.1007/s00709-011-0347-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2011] [Accepted: 10/18/2011] [Indexed: 05/31/2023]
Abstract
The couplons of the cardiomyocyte form nanospaces within the cell that place the L-type calcium channel (Ca(v)1.2), situated on the plasmalemma, in opposition to the type 2 ryanodine receptor (RyR2), situated on the sarcoplasmic reticulum. These two molecules, which form the basis of excitation-contraction coupling, are separated by a very limited space, which allows a few Ca(2+) ions passing through Ca(v)1.2 to activate the RyR2 at concentration levels that would be deleterious to the whole cell. The limited space also allows Ca(2+) inactivation of Ca(v)1.2. We have found that not all couplons are the same and that their properties are likely determined by their molecular partners which, in turn, determine their excitability. In particular, there are a class of couplons that lie outside the RyR2-Ca(v)1.2 dyad; in this case, the RyR2 is close to caveolin-3 rather than Ca(v)1.2. These extra-dyadic couplons are probably controlled by the multitude of molecules associated with caveolin-3 and may modulate contractile force under situations such as stress. It has long been assumed that like the skeletal muscle, the RyR2 in the couplon are arranged in a structured array with the RyR2 interacting with each other via domain 6 of the RyR2 molecule. This arrangement was thought to provide local control of RyR2 excitability. Using 3D electron tomography of the couplon, we show that the RyR2 in the couplon do not form an ordered pattern, but are scattered throughout it. Relatively few are in a checkerboard pattern--many RyR2 sit edge-to-edge, a configuration which might preclude their controlling each other's excitability. The discovery of this structure makes many models of cardiac couplon function moot and is a current avenue of further research.
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Affiliation(s)
- Parisa Asghari
- Department of Cellular and Physiological Sciences, University of British Columbia, Life Sciences Institute, 2350 Health Sciences Mall, Vancouver, BC, Canada
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38
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Dynamic changes in sarcoplasmic reticulum structure in ventricular myocytes. J Biomed Biotechnol 2011; 2011:382586. [PMID: 22131804 PMCID: PMC3206393 DOI: 10.1155/2011/382586] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Accepted: 08/09/2011] [Indexed: 11/23/2022] Open
Abstract
The fidelity of excitation-contraction (EC) coupling in ventricular myocytes is remarkable, with each action potential evoking a [Ca2+]i transient. The prevalent model is that the consistency in EC coupling in ventricular myocytes is due to the formation of fixed, tight junctions between the
sarcoplasmic reticulum (SR) and the sarcolemma where Ca2+ release is activated. Here, we tested the hypothesis that the SR is a structurally inert organelle in ventricular myocytes. Our data suggest that rather than being static, the SR undergoes frequent dynamic structural changes. SR boutons expressing functional ryanodine receptors moved throughout the cell, approaching or moving away from the sarcolemma of ventricular myocytes. These changes in SR structure occurred in the absence of changes in [Ca2+]i during EC coupling. Microtubules and the molecular motors dynein and kinesin 1(Kif5b) were important regulators of SR motility. These findings support a model in which the SR is a motile organelle capable of molecular motor protein-driven structural changes.
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Richards MA, Clarke JD, Saravanan P, Voigt N, Dobrev D, Eisner DA, Trafford AW, Dibb KM. Transverse tubules are a common feature in large mammalian atrial myocytes including human. Am J Physiol Heart Circ Physiol 2011; 301:H1996-2005. [PMID: 21841013 DOI: 10.1152/ajpheart.00284.2011] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Transverse (t) tubules are surface membrane invaginations that are present in all mammalian cardiac ventricular cells. The apposition of L-type Ca(2+) channels on t tubules with the sarcoplasmic reticulum (SR) constitutes a "calcium release unit" and allows close coupling of excitation to the rise in systolic Ca(2+). T tubules are virtually absent in the atria of small mammals, and therefore Ca(2+) release from the SR occurs initially at the periphery of the cell and then propagates into the interior. Recent work has, however, shown the occurrence of t tubules in atrial myocytes from sheep. As in the ventricle, Ca(2+) release in these cells occurs simultaneously in central and peripheral regions. T tubules in both the atria and the ventricle are lost in disease, contributing to cellular dysfunction. The aim of this study was to determine if the occurrence of t tubules in the atrium is restricted to sheep or is a more general property of larger mammals including humans. In atrial tissue sections from human, horse, cow, and sheep, membranes were labeled using wheat germ agglutinin. As previously shown in sheep, extensive t-tubule networks were present in horse, cow, and human atrial myocytes. Analysis shows half the volume of the cell lies within 0.64 ± 0.03, 0.77 ± 0.03, 0.84 ± 0.03, and 1.56 ± 0.19 μm of t-tubule membrane in horse, cow, sheep, and human atrial myocytes, respectively. The presence of t tubules in the human atria may play an important role in determining the spatio-temporal properties of the systolic Ca(2+) transient and how this is perturbed in disease.
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Affiliation(s)
- M A Richards
- Unit of Cardiac Physiology, University of Manchester, Core Technology Facility, Manchester, United Kingdom
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40
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Scriven DRL, Asghari P, Schulson MN, Moore EDW. Analysis of Cav1.2 and ryanodine receptor clusters in rat ventricular myocytes. Biophys J 2011; 99:3923-9. [PMID: 21156134 DOI: 10.1016/j.bpj.2010.11.008] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2010] [Revised: 11/03/2010] [Accepted: 11/05/2010] [Indexed: 11/26/2022] Open
Abstract
We analyzed the distribution of ryanodine receptor (RyR) and Cav1.2 clusters in adult rat ventricular myocytes using three-dimensional object-based colocalization metrics. We found that ∼75% of the Cav1.2 clusters and 65% of the RyR clusters were within couplons, and both were roughly two and a half times larger than their extradyadic counterparts. Within a couplon, Cav1.2 was concentrated near the center of the underlying RyR cluster and accounted for ∼67% of its size. These data, together with previous findings from binding studies, enable us to estimate that a couplon contains 74 RyR tetramers and 10 copies of the α-subunit of Cav1.2. Extradyadic clusters of RyR contained ∼30 tetramers, whereas the extradyadic Cav1.2 clusters contained, on average, only four channels. Between 80% and 85% of both RyR and Cav1.2 molecules are within couplons. RyR clusters were in the closest proximity, with a median nearest-neighbor distance of 552 nm; comparable values for Cav1.2 clusters and couplons were 619 nm and 735 nm, respectively. Extradyadic RyR clusters were significantly closer together (624 nm) and closer to the couplons (674 nm) than the couplons were to each other. In contrast, the extradyadic clusters of Cav1.2 showed no preferential localization and were broadly distributed. These results provide a wealth of morphometric data that are essential for understanding intracellular Ca2+ regulation and modeling Ca2+ dynamics.
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Affiliation(s)
- David R L Scriven
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
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41
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Chaanine AH, Kalman J, Hajjar RJ. Cardiac gene therapy. Semin Thorac Cardiovasc Surg 2011; 22:127-39. [PMID: 21092890 DOI: 10.1053/j.semtcvs.2010.09.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/03/2010] [Indexed: 11/11/2022]
Abstract
Heart failure is a chronic progressive disorder in which frequent and recurrent hospitalizations are associated with high mortality and morbidity. The incidence and the prevalence of this disease will increase with the increase in the number of the aging population of the United States. Understanding the molecular pathology and pathophysiology of this disease will uncover novel targets and therapies that can restore the function or attenuate the damage of malfunctioning cardiomyocytes by gene therapy that becomes an interesting and a promising field for the treatment of heart failure as well as other diseases in the future. Of equal importance are developing vectors and delivery methods that can efficiently transduce most of the cardiomyocytes that can offer a long-term expression and that can escape the host immune response. Recombinant adeno-associated virus vectors have the potential to become a promising novel therapeutic vehicles for molecular medicine in the future.
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Affiliation(s)
- Antoine H Chaanine
- Cardiovascular Institute, Mount Sinai School of Medicine, New York, New York 10029, USA
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42
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Escobar M, Cardenas C, Colavita K, Petrenko NB, Franzini-Armstrong C. Structural evidence for perinuclear calcium microdomains in cardiac myocytes. J Mol Cell Cardiol 2010; 50:451-9. [PMID: 21147122 DOI: 10.1016/j.yjmcc.2010.11.021] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Revised: 11/24/2010] [Accepted: 11/29/2010] [Indexed: 10/18/2022]
Abstract
At each heartbeat, cardiac myocytes are activated by a cytoplasmic Ca(2+) transient in great part due to Ca(2+) release from the sarcoplasmic reticulum via ryanodine receptors (RyRs) clustered within calcium release units (peripheral couplings/dyads). A Ca(2+) transient also occurs in the nucleoplasm, following the cytoplasmic transient with some delay. Under conditions where the InsP3 production is stimulated, these Ca(2+) transients are regulated actively, presumably by an additional release of Ca(2+) via InsP3 receptors (InsP3Rs). This raises the question whether InsP3Rs are appropriately located for this effect and whether sources of InsP3 and Ca(2+) are available for their activation. We have defined the structural basis for InsP3R activity at the nucleus, using immunolabeling for confocal microscopy and freeze-drying/shadowing, T tubule "staining" and thin sectioning for electron microscopy. By these means we establish the presence of InsP3R at the outer nuclear envelope and show a close spatial relationship between the nuclear envelope, T tubules (a likely source of InsP3) and dyads (the known source of Ca(2+)). The frequency, distribution and distance from the nucleus of T tubules and dyads appropriately establish local perinuclear Ca(2+) microdomains in cardiac myocytes.
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Affiliation(s)
- Matias Escobar
- Department of Cell and Developmental Biology, University of Pennsylvania, Philadelphia, PA 19104-6058, USA
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43
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Santana LF, Navedo MF. Natural inequalities: why some L-type Ca2+ channels work harder than others. ACTA ACUST UNITED AC 2010; 136:143-7. [PMID: 20660657 PMCID: PMC2912067 DOI: 10.1085/jgp.200910391] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Luis F Santana
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA.
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44
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Cheng Y, Yu Z, Hoshijima M, Holst MJ, McCulloch AD, McCammon JA, Michailova AP. Numerical analysis of Ca2+ signaling in rat ventricular myocytes with realistic transverse-axial tubular geometry and inhibited sarcoplasmic reticulum. PLoS Comput Biol 2010; 6:e1000972. [PMID: 21060856 PMCID: PMC2965743 DOI: 10.1371/journal.pcbi.1000972] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2009] [Accepted: 09/23/2010] [Indexed: 12/21/2022] Open
Abstract
The t-tubules of mammalian ventricular myocytes are invaginations of the cell membrane that occur at each Z-line. These invaginations branch within the cell to form a complex network that allows rapid propagation of the electrical signal, and hence synchronous rise of intracellular calcium (Ca2+). To investigate how the t-tubule microanatomy and the distribution of membrane Ca2+ flux affect cardiac excitation-contraction coupling we developed a 3-D continuum model of Ca2+ signaling, buffering and diffusion in rat ventricular myocytes. The transverse-axial t-tubule geometry was derived from light microscopy structural data. To solve the nonlinear reaction-diffusion system we extended SMOL software tool (http://mccammon.ucsd.edu/smol/). The analysis suggests that the quantitative understanding of the Ca2+ signaling requires more accurate knowledge of the t-tubule ultra-structure and Ca2+ flux distribution along the sarcolemma. The results reveal the important role for mobile and stationary Ca2+ buffers, including the Ca2+ indicator dye. In agreement with experiment, in the presence of fluorescence dye and inhibited sarcoplasmic reticulum, the lack of detectible differences in the depolarization-evoked Ca2+ transients was found when the Ca2+ flux was heterogeneously distributed along the sarcolemma. In the absence of fluorescence dye, strongly non-uniform Ca2+ signals are predicted. Even at modest elevation of Ca2+, reached during Ca2+ influx, large and steep Ca2+ gradients are found in the narrow sub-sarcolemmal space. The model predicts that the branched t-tubule structure and changes in the normal Ca2+ flux density along the cell membrane support initiation and propagation of Ca2+ waves in rat myocytes. In cardiac muscle cells, calcium (Ca2+) is best known for its role in contraction activation. A remarkable amount of quantitative data on cardiac cell structure, ion-transporting protein distributions and intracellular Ca2+ dynamics has been accumulated. Various alterations in the protein distributions or cell ultra-structure are now recognized to be the primary mechanisms of cardiac dysfunction in a diverse range of common pathologies including cardiac arrhythmias and hypertrophy. Using a 3-D computational model, incorporating more realistic transverse-axial t-tubule geometry and considering geometric irregularities and inhomogeneities in the distribution of ion-transporting proteins, we analyze several important spatial and temporal features of Ca2+ signaling in rat ventricular myocytes. This study demonstrates that the computational models could serve as powerful tools for prediction and analyses of how the Ca2+ dynamics and cardiac excitation-contraction coupling are regulated under normal conditions or certain pathologies. The use of computational and mathematical approaches will help also to better understand aspects of cell functions that are not currently amenable to experimental investigation.
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Affiliation(s)
- Yuhui Cheng
- Department of Bioengineering, University of California San Diego, La Jolla, California, United States of America
| | - Zeyun Yu
- Department of Computer Science, University of Wisconsin, Milwaukee, Wisconsin, United States of America
| | - Masahiko Hoshijima
- Department of Medicine, University of California San Diego, La Jolla, California, United States of America
| | - Michael J. Holst
- Department of Mathematics, University of California San Diego, La Jolla, California, United States of America
| | - Andrew D. McCulloch
- Department of Bioengineering, University of California San Diego, La Jolla, California, United States of America
| | - J. Andrew McCammon
- Department of Chemistry and Biochemistry, Department of Pharmacology, University of California San Diego, La Jolla, California, United States of America
- Howard Hughes Medical Institute, University of California San Diego, La Jolla, California, United States of America
| | - Anushka P. Michailova
- Department of Bioengineering, University of California San Diego, La Jolla, California, United States of America
- * E-mail:
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Franzini-Armstrong C. RyRs: Their Disposition, Frequency, and Relationships with Other Proteins of Calcium Release Units. CURRENT TOPICS IN MEMBRANES 2010; 66:3-26. [PMID: 22353474 DOI: 10.1016/s1063-5823(10)66001-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/09/2022]
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46
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Fink M, Niederer SA, Cherry EM, Fenton FH, Koivumäki JT, Seemann G, Thul R, Zhang H, Sachse FB, Beard D, Crampin EJ, Smith NP. Cardiac cell modelling: observations from the heart of the cardiac physiome project. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2010; 104:2-21. [PMID: 20303361 DOI: 10.1016/j.pbiomolbio.2010.03.002] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2009] [Revised: 12/06/2009] [Accepted: 03/04/2010] [Indexed: 10/19/2022]
Abstract
In this manuscript we review the state of cardiac cell modelling in the context of international initiatives such as the IUPS Physiome and Virtual Physiological Human Projects, which aim to integrate computational models across scales and physics. In particular we focus on the relationship between experimental data and model parameterisation across a range of model types and cellular physiological systems. Finally, in the context of parameter identification and model reuse within the Cardiac Physiome, we suggest some future priority areas for this field.
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Affiliation(s)
- Martin Fink
- Department of Physiology, Anatomy and Genetics, University of Oxford, OX1 3JP, United Kingdom
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47
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A new twist in cardiac muscle: dislocated and helicoid arrangements of myofibrillar z-disks in mammalian ventricular myocytes. J Mol Cell Cardiol 2010; 48:964-71. [PMID: 20045003 DOI: 10.1016/j.yjmcc.2009.12.012] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2009] [Revised: 12/02/2009] [Accepted: 12/17/2009] [Indexed: 11/21/2022]
Abstract
Using deconvolved confocal microscopy of fluorescently labeled markers for z-disks, t-tubules and ryanodine receptors, we have examined sarcomere organization in cardiac myocytes from rat, rabbit and human. We show that sarcomeres exhibit dislocations in registration and occasionally more complex helicoidal topology. This organization was present at both slack ( approximately 1.8 microm) and long sarcomere lengths ( approximately 2.2 microm). Misregistrations in z-disks persisted over 15-20 sarcomere lengths and appeared to arise primarily from variations in fiber direction; particularly as myofibrils pass around nuclei. In addition, myofibrils twist along the cell length. T-tubules generally follow the sarcomere z-disks although additional elements bridging adjacent myofibrils and along the length of the myofibril are present to varying degrees in all cells. Ryanodine receptors (the sarcoplasmic reticulum Ca(2+) release channel) are generally located within 250 nm of the local plane containing t-tubules and z-disks, but a small fraction ( approximately 2%) is found on longitudinal elements of the t-system between z-disks. The results are discussed with respect to the possible role(s) of such complex z-disk organization and z-disk dislocations in the maintenance of cell structure and sarcomere assembly. In addition, the non-planar organization of z-disks may be important in the propagation of local Ca(2+) waves which may have a useful role in helping maintain the uniformity of sarcomere activation in the presence of t-tubule remodeling.
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48
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Baddeley D, Jayasinghe ID, Lam L, Rossberger S, Cannell MB, Soeller C. Optical single-channel resolution imaging of the ryanodine receptor distribution in rat cardiac myocytes. Proc Natl Acad Sci U S A 2009; 106:22275-80. [PMID: 20018773 PMCID: PMC2799702 DOI: 10.1073/pnas.0908971106] [Citation(s) in RCA: 224] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2009] [Indexed: 11/18/2022] Open
Abstract
We have applied an optical super-resolution technique based on single-molecule localization to examine the peripheral distribution of a cardiac signaling protein, the ryanodine receptor (RyR), in rat ventricular myocytes. RyRs form clusters with a mean size of approximately 14 RyRs per cluster, which is almost an order of magnitude smaller than previously estimated. Clusters were typically not circular (as previously assumed) but elongated with an average aspect ratio of 1.9. Edge-to-edge distances between adjacent RyR clusters were often <50 nm, suggesting that peripheral RyR clusters may exhibit strong intercluster signaling. The wide variation of cluster size, which follows a near-exponential distribution, is compatible with a stochastic cluster assembly process. We suggest that calcium sparks may be the result of the concerted activation of several RyR clusters forming a functional "supercluster" whose gating is controlled by both cytosolic and sarcoplasmic reticulum luminal calcium levels.
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Affiliation(s)
- David Baddeley
- Department of Physiology, University of Auckland, Auckland 1142, New Zealand
| | - Isuru D. Jayasinghe
- Department of Physiology, University of Auckland, Auckland 1142, New Zealand
| | - Leo Lam
- Department of Physiology, University of Auckland, Auckland 1142, New Zealand
| | - Sabrina Rossberger
- Department of Physiology, University of Auckland, Auckland 1142, New Zealand
| | - Mark B. Cannell
- Department of Physiology, University of Auckland, Auckland 1142, New Zealand
| | - Christian Soeller
- Department of Physiology, University of Auckland, Auckland 1142, New Zealand
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